U.S. patent application number 10/197764 was filed with the patent office on 2003-07-31 for water-soluble preflux, printed circuit board, and process for treating the surface of a metal in a printed circuit board.
Invention is credited to Akaike, Shinichi, Nakanami, Kazutaka, Ono, Takao, Takahashi, Yoshiyuki.
Application Number | 20030141351 10/197764 |
Document ID | / |
Family ID | 19053012 |
Filed Date | 2003-07-31 |
United States Patent
Application |
20030141351 |
Kind Code |
A1 |
Akaike, Shinichi ; et
al. |
July 31, 2003 |
Water-soluble preflux, printed circuit board, and process for
treating the surface of a metal in a printed circuit board
Abstract
The invention provides a water-soluble prefluxe that can solve
problems with a soldering land array having a narrow spacing in
that fused solder is likely to cause soldering bridges with
defective soldering, a printed circuit board with its film formed
thereon, and a surface treatment process for a metal in that
circuit. The water-soluble preflus comprises given two different
benzimidazoles compound and an iodine-based compound optionally
with an amino acid, etc. The invention provides a printed circuit
board with a film of that preflux formed thereon, and a surface
treatment process for the metal in that circuit.
Inventors: |
Akaike, Shinichi; (Saitama,
JP) ; Nakanami, Kazutaka; (Saitama, JP) ;
Takahashi, Yoshiyuki; (Saitama, JP) ; Ono, Takao;
(Saitama, JP) |
Correspondence
Address: |
KING & SCHICKLI, PLLC
247 NORTH BROADWAY
LEXINGTON
KY
40507
US
|
Family ID: |
19053012 |
Appl. No.: |
10/197764 |
Filed: |
July 18, 2002 |
Current U.S.
Class: |
228/207 |
Current CPC
Class: |
H05K 3/282 20130101;
B23K 35/3615 20130101; C23F 11/08 20130101; C23F 11/149 20130101;
B23K 35/3616 20130101 |
Class at
Publication: |
228/207 |
International
Class: |
B23K 031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2001 |
JP |
2001-218911 |
Claims
What is claimed is:
1. A water-soluble preflux comprising at least one compound
selected from the group consisting of compounds represented by the
following general formulae (1) and (3), at least one compound
having the following general formula (2), and an iodine-based
compound: Formula (1) 40where R.sub.1 is a straight-chain or
branched-chain alkyl group having 1 to 7 carbon atoms, a halogen
atom, an amino group, a di-lower alkylamino group, a hydroxy group,
a lower alkoxy group, a cyano group, an acetyl group, a benzoyl
group, a carbamoyl group, a formyl group, a carboxyl group, a lower
alkoxycarbonyl group or a nitro group with the proviso that when
R.sub.1 represents two or more groups, they may be different from
or identical with each other, R.sub.2 is a straight-chain or
branched-chain alkyl group, R.sub.3 is a phenyl group or an
alkylphenyl group with the proviso that when R.sub.3 represents two
or more groups, they may be different from or identical with each
other, n is an integer of 0 to 4, and m is an integer of 0 to 3;
Formula (2) 41where each of R.sub.4 and R.sub.5 is a straight-chain
or branched-chain alkyl group having 1 to 7 carbon atoms, a halogen
atom, an amino group, a di-lower alkylamino group, a hydroxy group,
a lower alkoxy group, a cyano group, an acetyl group, a benzoyl
group, a carbamoyl group, a formyl group, a carboxyl group, a lower
alkoxycarbonyl group or a nitro group with the proviso that when
each of R.sub.4 and R.sub.5 represents two or more groups, they may
be different from or identical with each other, R.sub.5 may be a
straight-chain or branched-chain alkyl group, a phenyl group, an
alkylphenyl group or an phenylalkyl group with the proviso that
when R.sub.5 represents two or more groups, they may be different
from or identical with each other, n is an integer of 0 to 4, m is
an integer of 0 to 10, and p is an integer of 0 to 4; and Formula
(3) 42where R is a straight-chain or branched-chain alkyl group
having 1 to 7 carbon atoms with the proviso that when R represents
two or more groups, they may be different from or identical with
each other, R.sub.6 is a straight-chain or branched-chain alkyl
group having 1 to 7 carbon atoms with the proviso that when R.sub.6
represents two or more groups, they may be different from or
identical with each other, n is an integer of 0 to 3, m is an
integer of 0 to 4, p is an integer of 0 to 3, and q is an integer
of 0 to 4.
2. A water-soluble preflux comprising at least one compound
selected from the group consisting of compounds represented by the
aforesaid formulae (1) and (3), at least one compound represented
by the aforesaid general formula (2), an iodine-based compound, and
an amine-based compound.
3. The water-soluble preflux according to claim 1 or 2, wherein the
ratio of at least one compound selected from the group consisting
of compounds represented by the aforesaid general formulae (1) and
(3) used with respect to at least one compound represented by the
aforesaid general formula (2) is in the range of 0.5 to 5 on a mass
basis.
4. The water-soluble preflux according to claim 2 or 3, wherein the
amine-based compound is a solubilizer comprising at least one of
heterocyclic rings having a ring containing a primary amino group,
a secondary amino group, a tertiary amino group and a nitrogen atom
capable of forming an insoluble salt with at least one compound
selected from the group consisting of compounds represented by the
aforesaid general formulae (1) and (3) and at least one compound
represented by the aforesaid general formula (2) and having an
acidic group.
5. The water-soluble preflux according to any one of claims 1 to 4,
wherein the iodine-base compound is at least one selected from the
group consisting of hydriodic acid, a metal salt of hydriodic acid
and an iodized organic acid.
6. The water-soluble preflux according to claim 4 or 5, wherein the
solubilizer comprises at least one compound selected from the group
consisting of compounds represented by the following general
formulae (11) to (16), L-theanine, pyroglutamic acid,
pyrrolidine-2,4-dicarboxylic acid, folic acid, DL-threonine,
L-threonine, L-tryptophan, L-phenylalanine and quinaldinic acid and
their derivatives: Formula (11) 43where R.sub.7 is a straight-chain
or branched-chain alkyl group having 1 to 20 carbon atoms, a
halogen atom, a hydroxyl group, a lower alkoxyl group, a cyano
group, an acetyl group, a benzoyl group, a carbamoyl group, a
formyl group or a nitro group with the proviso that when R.sub.7
represents two or more groups, they may be different from or
identical with each other, R.sub.8 may be zero, and is a
straight-chain or branched-chain alkylene group having 1 to 20
carbon atoms with the proviso that when R.sub.8 represents two or
more groups, they may be different from or identical with each
other, n is an integer of 0 to 4, and m is an integer of 1 to 5;
Formula (12) 44where R.sub.9 is a straight-chain or branched-chain
alkyl group having 1 to 20 carbon atoms, a halogen atom, a hydroxyl
group, a lower alkoxyl group, a cyano group, an acetyl group, a
benzoyl group, a carbamoyl group, a formyl group or a nitro group
with the proviso that when R.sub.9 represents two or more groups,
they may be different from or identical with each other, R.sub.10
may be zero, and is a straight-chain or branched-chain alkylene
group having 1 to 20 carbon atoms with the proviso that when
R.sub.10 represents two or more groups, they may be different from
or identical with each other, n is an integer of 0 to 4, and m is
an integer of 1 to 5; Formula (13) 45where R.sub.11 is a
straight-chain or branched-chain alkyl group having 1 to 20 carbon
atoms, a halogen atom, a hydroxyl group, a lower alkoxyl group, a
cyano group, an acetyl group, a benzoyl group, a carbamoyl group, a
formyl group or a nitro group with the proviso that when R.sub.11
represents two or more groups, they may be different from or
identical with each other, R.sub.12 may be zero, and is a
straight-chain or branched-chain alkylene group having 1 to 20
carbon atoms with the proviso that when R.sub.12 represents two or
more groups, they may be different from or identical with each
other, n is an integer of 0 to 3, and m is an integer of 1 to 4;
Formula (14) 46where R.sub.13 is a straight-chain or branched-chain
alkyl group having 1 to 20 carbon atoms, a halogen atom, a hydroxyl
group, a lower alkoxyl group, a cyano group, an acetyl group, a
benzoyl group, a carbamoyl group, a formyl group or a nitro group
with the proviso that when R.sub.13 represents two or more groups,
they may be different from or identical with each other, R.sub.14
may be zero, and is a straight-chain or branched-chain alkylene
group having 1 to 20 carbon atoms with the proviso that when
R.sub.14 represents two or more groups, they may be different from
or identical with each other, n is an integer of 0 to 3, and m is
an integer of 1 to 4; Formula
(15)(R.sub.15).sub.n--N--(R.sub.16--COOH).sub.mwhere R.sub.15 is a
hydrogen atom, a straight-chain or branched-chain alkyl group
having 1 to 20 carbon atoms, a halogen atom, a hydroxyl group, a
lower alkoxyl group, a cyano group, an acetyl group, a benzoyl
group, a carbamoyl group, a formyl group or a nitro group with the
proviso that when R.sub.15 represents two or more groups, they may
be different from or identical with each other, R.sub.16 may be
zero, and is a straight-chain or branched-chain alkylene group
having 1 to 20 carbon atoms with the proviso that when R.sub.16
represents two or more groups, they may be different from or
identical with each other, n is an integer of 0 to 2, and m is an
integer of 1 to 3; and Formula (16) 47where R.sub.17 is a hydrogen
atom, a straight-chain or branched-chain alkyl group having 1 to 20
carbon atoms, a halogen atom, a hydroxyl group, a lower alkoxyl
group, a cyano group, an acetyl group, a benzoyl group, a carbamoyl
group, a formyl group or a nitro group with the proviso that when
R.sub.17 represents two, they may be different from or identical
with each other, R.sub.19 is a hydrogen atom, a straight-chain or
branched-chain alkyl group having 1 to 20 carbon atoms, a halogen
atom, a hydroxyl group, a lower alkoxyl group, a cyano group, an
acetyl group, a benzoyl group, a carbamoyl group, a formyl group or
a nitro group with the proviso that when R.sub.19 represents two,
they may be different from or identical with each other, R.sub.18
may be zero, and is a straight-chain or branched-chain alkylene
group having 1 to 20 carbon atoms with the proviso that when
R.sub.18 represents two groups, they may be different from or
identical with each other, R.sub.20 may be zero, and is a
straight-chain or branched-chain alkylene group having 1 to 20
carbon atoms with the proviso that when R.sub.20 represents two
groups, they may be different from or identical with each other, n
is an integer of 0 to 2, m is an integer of 0 to 2, p is an integer
of 0 to 4, q is an integer of 0 to 1, and r is an integer of 1 to
2.
7. A printed circuit board having a metal layer for a circuit
pattern on its surface, wherein said metal layer comprises a film
of a water-soluble preflux as recited in any one of claims 1 to
6.
8. A surface treatment process for a metal in a printed circuit
board, wherein a metal layer for a circuit pattern on a printed
circuit board is subjected to rust-preventive treatment by a step
of coating thereon a water-soluble preflux as recited in any one of
claims 1 to 6.
Description
TECHNICAL FIELD
[0001] The present invention relates to a water-soluble preflux
containing a water-soluble salt of a benzimidazole-based compound,
which can improve the wetting coverage of fused solder during
soldering in particular, a printed circuit board having a film of
such a preflux formed thereon, and a process for the surface
treatment of metals in printed circuit boards.
BACKGROUND OF THE INVENTION
[0002] A printed circuit board, comprising a copper-clad laminate
board as an example and a printed circuit pattern formed thereon,
is designed to form one single circuit unit by mounting electronic
parts thereon.
[0003] For such a printed circuit board, there is often used a
surface mount type that comprises a circuit pattern with circuit
interconnections formed on the surface of a board and electronic
parts mounted on the circuit pattern. For instance, when a chip
part having electrodes at both ends is used as an electronic part,
a flux is first coated on the printed circuit board, and the chip
part is then soldered to the printed circuit board by means of a
wave soldering process or a reflow soldering process.
[0004] For soldering of such chip parts, there is generally used a
soldering process wherein after a circuit pattern is formed on a
printed circuit board, i.e., a copper foil portion of a copper-clad
laminate board is etched in such a way that the desired circuit
interconnections are obtained, a solder resist film is coated on
the obtained circuit except a portion thereof to which a chip part
is soldered, i.e., so-called soldering lands, and micro etching is
further carried out, immediately after which soldering is
performed. In some cases, however, the steps including coating by a
solder resist film and the subsequent soldering step are
independently carried out, so that the soldering step can be
performed after the solder resist film-coated printed circuit board
is stored as a part or by other soldering experts in the process of
circulation. In such a case, much time has lapsed until the
soldering step is actually carried out. In this period, the exposed
copper foil surface of the soldering lands is susceptible to
oxidation by air, and this oxidation is more likely to occur in
damp environments. To prevent oxidation of that surface, an
oxidation-preventive film is formed thereon and a surface
protective agent is used to this end.
[0005] Even when a printed circuit board coated with a solder
resist film is used just after its fabrication, an
oxidation-preventive film should be formed. This is because when a
reflow soldering process, for instance, is used to mount electronic
parts on both surfaces of a printed circuit board, solder powders
are fused by heating at high temperatures such as 260.degree. C.
after a solder paste is coated on the soldering lands and,
consequently, when one surface is soldered, other surface is
exposed to high temperatures at which the copper foil surface of
the soldering lands is susceptible to oxidation. In such a case,
too, an oxidation-preventive film should be formed.
[0006] Either when such surface-preventive agent treatment is
carried out or when the other surfaces of the soldering lands are
subjected to oxidation-preventive treatment so as to prevent
deterioration upon heating which may otherwise be caused in
association with the soldering of one surface of the printed
circuit board, so-called prefluxes are used, among which organic
solvent-free, water-soluble ones are preferably used because of no
risk of pollutions or fires.
[0007] So far, the exposed copper foil of soldering lands has been
subjected to rust-preventive treatment. As set forth typically in
Japanese patent unexamined publication No. 05-25407 and No.
05-186888, it has been known that water-soluble surface-preventive
agents for printed circuit boards containing a benzimidazole-based
compound are used as water-soluble prefluxes. According to these
publications, a printed board with a copper foil circuit pattern
formed on its surface is immersed in the water-soluble
surface-protective agent for printed circuit boards to, form a
heat-resistant film on the surface of copper and a copper alloy of
the circuit pattern on the printed circuit board. This film has
also extremely satisfactory humidity resistance even upon exposed
to high humidity; it is considerably improved in terms of
protection of printed circuit boards and solderability at the time
of part mounting. Thus, these surface-protective agents are found
to be more improved in terms of productivity, performance, etc., as
compared with prefluxes containing rosin or the like, which cause
coating films to be formed on portions other than copper foil
portions, and make it impossible to give high reliability to
circuits without rinsing or pickling boards after parts are mounted
thereon.
[0008] The compound used to improve this surface-preventive agent
preflux, i.e., the benzimidazole-based compound that is the primary
component of the surface-preventive agent for printed circuit
boards is generally insoluble in water, and so is made soluble by
using inorganic acids such as hydrochloric acid and phosphoric acid
or organic acids such as acetic acid, oxalic acid and
p-toluene-sulfonic acid as solubilizers for forming its
water-soluble salt. The acids used as such solubilizers erode a
particularly sensitive-to-acid lead film to render its thickness
small or oxidizes its surface, often rendering it impossible to
obtain the given soldering strength for lead wires at the time of
part mounting and poor soldering as well, which may otherwise give
rise to some considerable mounting yield drops. Allegedly, this
problem may be solved by using an amino acid as the solubilizer
thereby making benzimidazole-based compounds soluble in water
without recourse to the aforesaid acids, as set forth in Japanese
patent unexamined publication No. 05-186888.
[0009] Even when water-soluble prefluxes composed primarily of
these benzimidazole-based compounds are used, however, much is
still left to be desired in terms of the wetting coverage of fused
solder when a solder paste is coated on soldering lands and heated
to fuse solder powders.
[0010] As recent electronic parts slim down with enhanced
performance, printed circuit boards in particular are now required
to have performance keeping pace with high-density packaging for
mounting electronic parts at high density. With this, it is
demanded to enable electronic parts to be well soldered to a
soldering land array having a much narrower spacing of the order of
0.3 to 0.4 mm. As a solder paste is coated and heated on a
soldering land array having a narrow spacing, however, some
portions of fused solder formed by fusion of solder powders come
into contact with each other on the respective soldering lands.
These portions, if they are cooled down as such, often form
together a soldering bridge that offers a short-circuit problem,
ending up with poorly soldered, defective board products. For those
who are required to achieve fierce production cost reductions, it
is thus of vital importance to cut back on the incidence of
soldering bridges that may occur upon fusion of the aforesaid
solder paste film, thereby achieving productivity improvements.
[0011] From this point-of-view, there is thus available a process
wherein a smaller amount of solder paste than usual is coated on a
portion of a soldering land except both its end portions rather
than all over the soldering land in such a controlled way that when
solder powders are fused and concentrated centrally on that portion
into a liquid droplet, the size of the liquid droplet is kept from
becoming excessively large, whereby fused solder on that portion is
prevented from contact with fused solder similarly formed on the
adjacent lands. In this case, however, the reduced amount of solder
presents another grave problem in that any desired soldering
strength is not obtained.
[0012] The first object of the present invention is to provide a
water-soluble preflux that enables fused solder to be well wetted
to and spread over a soldering land array in general and a
soldering land array having a narrow spacing in particular, a
printed circuit board, and a surface treatment process for a metal
on a printed circuit board.
[0013] The second object of the present invention is to provide a
water-soluble preflux that enables fused solder to be well wetted
to and spread over a soldering land array which degrades upon
heated to high temperature for the purpose of double-sided
mounting, etc., a printed circuit board, and a surface treatment
process for a metal on a printed circuit board.
[0014] The third object of the present invention is to provide a
water-soluble preflux that can cut down on the incidence of
soldering bridges and ensures sufficient soldering strength so that
defects upon soldering can be reduced with productivity
improvements, a printed circuit board, and a surface treatment
process for a metal on a printed circuit board.
[0015] The fourth object of the present invention is to provide a
water-soluble preflux that enables a benzimidazole-based compound
to be solubilized without recourse to an ordinarily used acid, a
printed circuit board, and a surface treatment process for a metal
on a printed circuit board.
[0016] The fifth object of the present invention is to provide a
water-soluble preflux that can form a film having much more
improved humidity resistance even after exposed to high humidity
and is much more improved in terms of protection of a printed
circuit board and solderability at the time of part mounting, a
printed circuit board, and a surface treatment process for a metal
on a printed circuit board.
[0017] The sixth object of the present invention is to provide a
water-soluble preflux that is free from defects that when an acid
employed so far as a solubilizer is used, there is a soldering
strength drop due to oxidation of solder, erosion of lead, etc., a
printed circuit board, and a surface treatment process for a metal
on a printed circuit board.
[0018] The seventh object of the present invention is to provide a
water-soluble preflux to which a production process and a
utilization process similar to those for conventional water-soluble
prefluxes using benzimidazole-based compounds, a printed circuit
board, and a surface treatment process for a metal on a printed
circuit board.
[0019] The eighth object of the present invention is to provide a
water-soluble preflux that can prevent each of the components used
from becoming instable due to temperature changes and working
environments from becoming worse due to volatile acids, a printed
circuit board, and a surface treatment process for a metal on a
printed circuit board.
[0020] As a result of intensive studies made to attain the
aforesaid objects, the inventors have found that if the wetting
coverage of fused solder with respect to soldering lands with a
water-soluble preflux film coated thereon is enlarged, it is then
possible to obtain the given soldering strength even when the
amount of fused solder, i.e., the amount of the solder paste to be
coated is reduced, and prevent fused solder on a certain soldering
land from coming into contact with similar fused solder on the
adjacent soldering lands, thereby avoiding any soldering bridge.
Such findings have underlain the present invention.
SUMMARY OF THE INVENTION
[0021] According to the first aspect of the invention, there is
provided a water-soluble preflux comprising at least one compound
selected from the group consisting of compounds represented by the
following general formulae (1) and (3), at least one compound
having the following general formula (2), and an iodine-based
compound.
[0022] Formula (1) 1
[0023] Here R.sub.1 is a straight-chain or branched-chain alkyl
group having 1 to 7 carbon atoms, a halogen atom, an amino group, a
di-lower alkylamino group, a hydroxy group, a lower alkoxy group, a
cyano group, an acetyl group, a benzoyl group, a carbamoyl group, a
formyl group, a carboxyl group, a lower alkoxycarbonyl group or a
nitro group with the proviso that when R.sub.1 represents two or
more groups, they may be different from or identical with each
other, R.sub.2 is a straight-chain or branched-chain alkyl group,
R.sub.3 is a phenyl group or an alkylphenyl group with the proviso
that when R.sub.3 represents two or more groups, they may be
different from or identical with each other, n is an integer of 0
to 4, and m is an integer of 0 to 3.
[0024] Formula (2) 2
[0025] Here each of R.sub.4 and R.sub.5 is a straight-chain or
branched-chain alkyl group having 1 to 7 carbon atoms, a halogen
atom, an amino group, a di-lower alkylamino group, a hydroxy group,
a lower alkoxy group, a cyano group, an acetyl group, a benzoyl
group, a carbamoyl group, a formyl group, a carboxyl group, a lower
alkoxycarbonyl group or a nitro group with the proviso that when
R.sub.4 represents two or more groups, they may be different from
or identical with each other, R.sub.5 may be a straight-chain or
branched-chain alkyl group, a phenyl group, an alkylphenyl group or
an phenylalkyl group with the proviso that when R.sub.5 represents
two or more groups, they may be different from or identical with
each other, n is an integer of 0 to 4, m is an integer of 0 to 10,
and p is an integer of 0 to 4.
[0026] Formula (3) 3
[0027] Here R is a straight-chain or branched-chain alkyl group
having 1 to 7 carbon atoms with the proviso that when R represents
two or more groups, they may be different from or identical with
each other, R.sub.6 is a straight-chain or branched-chain alkyl
group having 1 to 7 carbon atoms with the proviso that when R.sub.6
represents two or more groups, they may be different from or
identical with each other, n is an integer of 0 to 3, m is an
integer of 0 to 4, p is an integer of 0 to 3, and q is an integer
of 0 to 4.
[0028] According to the second aspect of the invention, there is
provided a water-soluble preflux comprising at least one compound
selected from the group consisting of compounds represented by the
aforesaid formulae (1) and (3), at least one compound represented
by the aforesaid general formula (2), an iodine-based compound, and
an amine-based compound.
[0029] According to the third aspect of the invention, there is
provided a preflux of the first or second aspect, wherein the ratio
of at least one compound selected from the group consisting of
compounds represented by the aforesaid general formulae (1) and (3)
used with respect to at least one compound represented by the
aforesaid general formula (2) is in the range of 0.5 to 5 on a mass
basis.
[0030] According to the fourth aspect of the invention, there is
provided a water-soluble preflux of the second or third aspect,
wherein the amine-based compound is a solubilizer comprising at
least one of heterocyclic rings having a ring containing a primary
amino group, a secondary amino group, a tertiary amino group and a
nitrogen atom capable of forming an insoluble salt with at least
one compound selected from the group consisting of compounds
represented by the aforesaid general formulae (1) and (3) and at
least one compound represented by the aforesaid general formula (2)
and having an acidic group.
[0031] According to the fifth aspect of the invention, there is
provided a water-soluble preflux of any one of the first to fourth
aspects, wherein the iodine-base compound is at least one selected
from the group consisting of hydriodic acid, a metal salt of
hydriodic acid and an iodized organic acid.
[0032] According to the sixth aspect of the invention, there is
provided a water-soluble preflux of the fourth or fifth aspect,
wherein the solubilizer comprises at least one compound selected
from the group consisting of compounds represented by the following
general formulae (11) to (16), L-theanine, pyroglutamic acid,
pyrolidine-2,4-dicarboxylic acid, folic acid, DL-threonine,
L-threonine, L-tryptophan, L-phenylalanine and quinaldinic acid and
their derivatives.
[0033] Formula (11) 4
[0034] Here R.sub.7 is a straight-chain or branched-chain alkyl
group having 1 to 20 carbon atoms, a halogen atom, a hydroxyl
group, a lower alkoxyl group, a cyano group, an acetyl group, a
benzoyl group, a carbamoyl group, a formyl group or a nitro group
with the proviso that when R.sub.7 represents two or more groups,
they may be different from or identical with each other, R.sub.8
may be zero, and is a straight-chain or branched-chain alkylene
group having 1 to 20 carbon atoms with the proviso that when
R.sub.8 represents two or more groups, they may be different from
or identical with each other, n is an integer of 0 to 4, and m is
an integer of 1 to 5.
[0035] Formula (12) 5
[0036] Here R.sub.9 is a straight-chain or branched-chain alkyl
group having 1 to 20 carbon atoms, a halogen atom, a hydroxyl
group, a lower alkoxyl group, a cyano group, an acetyl group, a
benzoyl group, a carbamoyl group, a formyl group or a nitro group
with the proviso that when R.sub.9 represents two or more groups,
they may be different from or identical with each other, R.sub.10
may be zero, and is a straight-chain or branched-chain alkylene
group having 1 to 20 carbon atoms with the proviso that when
R.sub.10 represents two or more groups, they may be different from
or identical with each other, n is an integer of 0 to 4, and m is
an integer of 1 to 5.
[0037] Formula (13) 6
[0038] Here R.sub.11 is a straight-chain or branched-chain alkyl
group having 1 to 20 carbon atoms, a halogen atom, a hydroxyl
group, a lower alkoxyl group, a cyano group, an acetyl group, a
benzoyl group, a carbamoyl group, a formyl group or a nitro group
with the proviso that when R.sub.11 represents two or more groups,
they may be different from or identical with each other, R.sub.12
may be zero, and is a straight-chain or branched-chain alkylene
group having 1 to 20 carbon atoms with the proviso that when
R.sub.12 represents two or more groups, they may be different from
or identical with each other, n is an integer of 0 to 3, and m is
an integer of 1 to 4.
[0039] Formula (14) 7
[0040] Here R.sub.13 is a straight-chain or branched-chain alkyl
group having 1 to 20 carbon atoms, a halogen atom, a hydroxyl
group, a lower alkoxyl group, a cyano group, an acetyl group, a
benzoyl group, a carbamoyl group, a formyl group or a nitro group
with the proviso that when R.sub.13 represents two or more groups,
they may be different from or identical with each other, R.sub.14
may be zero, and is a straight-chain or branched-chain alkylene
group having 1 to 20 carbon atoms with the proviso that when
R.sub.12 represents two or more groups, they may be different from
or identical with each other, n is an integer of 0 to 3, and m is
an integer of 1 to 4.
[0041] Formula (15)
(R.sub.15).sub.n--N--(R.sub.16--COOH).sub.m
[0042] Here R.sub.15 is a hydrogen atom, a straight-chain or
branched-chain alkyl group having 1 to 20 carbon atoms, a halogen
atom, a hydroxyl group, a lower alkoxyl group, a cyano group, an
acetyl group, a benzoyl group, a carbamoyl group, a formyl group or
a nitro group with the proviso that when R.sub.15 represents two or
more groups, they may be different from or identical with each
other, R.sub.16 may be zero, and is a straight-chain or
branched-chain alkylene group having 1 to 20 carbon atoms with the
proviso that when R.sub.16 represents two or more groups, they may
be different from or identical with each other, n is an integer of
0 to 2, and m is an integer of 1 to 3.
[0043] Formula (16) 8
[0044] Here R.sub.17 is a hydrogen atom, a straight-chain or
branched-chain alkyl group having 1 to 20 carbon atoms, a halogen
atom, a hydroxyl group, a lower alkoxyl group, a cyano group, an
acetyl group, a benzoyl group, a carbamoyl group, a formyl group or
a nitro group with the proviso that when R.sub.17 represents two
groups, they may be different from or identical with each other,
R.sub.19 is a hydrogen atom, a straight-chain or branched-chain
alkyl group having 1 to 20 carbon atoms, a halogen atom, a hydroxyl
group, a lower alkoxyl group, a cyano group, an acetyl group, a
benzoyl group, a carbamoyl group, a formyl group or a nitro group
with the proviso that when R.sub.19 represents two groups, they may
be different from or identical with each other, R.sub.18 may be
zero, and is a straight-chain or branched-chain alkylene group
having 1 to 20 carbon atoms with the proviso that when R.sub.18
represents two groups, they may be different from or identical with
each other, R.sub.20 may be zero, and is a straight-chain or
branched-chain alkylene group having 1 to 20 carbon atoms with the
proviso that when R.sub.20 represents two groups, they may be
different from or identical with each other, n is an integer of 0
to 2, m is an integer of 0 to 2, p is an integer of 0 to 4, q is an
integer of 0 to 1, and r is an integer of 1 to 2.
[0045] According to the seventh aspect of the invention, there is
provided a printed circuit board having a metal layer for a circuit
pattern on its surface, wherein said metal layer comprises a film
of a water-soluble preflux as recited in any one of the aforesaid
first to sixth aspects.
[0046] According to the eighth aspect of the invention, there is
provided a surface treatment process for a metal in a printed
circuit board, wherein a metal layer for a circuit pattern on a
printed circuit board is subjected to rust-preventive treatment by
a step of coating thereon a water-soluble preflux as recited in any
one of the aforesaid first to sixth aspects.
DETAILED DESCRIPTION OF THE INVENTION
[0047] In the present invention, the preferable compounds belonging
to the aforesaid general formula (1), for instance, include those
represented by the following general formula (4).
[0048] Formula (4) 9
[0049] Here R.sub.11 is a straight-chain or branched-chain alkyl
group having 1 to 7 carbon atoms, a halogen atom, an amino group, a
di-lower alkylamino group, a hydroxy group, a lower alkoxy group, a
cyano group, an acetyl group, a benzoyl group, a carbamoyl group, a
formyl group, a carboxyl group, a lower alkoxycarbonyl group or a
nitro group with the proviso that when R.sub.11 represents two or
more groups, they may be different from or identical with each
other, R.sub.21 is a straight-chain or branched-chain alkyl group
having 1 to 20 carbon atoms, and n is an integer of 0 to 4.
[0050] Of the compounds belonging to this general formula (4),
preference is given to those represented by the following general
formula (5) as well as those represented by the following general
formulae (6) and (7) belonging to this general formula (5).
[0051] Formula (5) 10
[0052] Here R.sub.12 is a lower alkyl group with the proviso that
when R.sub.12 represents two groups, they may be different from or
identical with each other, R.sub.22 is a straight-chain or
branched-chain alkyl group having 3 to 17 carbon atoms, and n is an
integer of 1 to 2.
[0053] Formula (6) 11
[0054] Here n is an integer of 0 to 3.
[0055] 2-(1-ethylpentyl)benzimidazole,
2-(1-ethylpenthyl)tosylimidazole and
2-(1-ethylpentyl)xylylimidazole are exemplified.
[0056] Formula (7) 12
[0057] Here n is an integer of 0 to 3.
[0058] 2-(3-methylbutyl)benzimidazole,
2-(3-methylbutyl)tosylimidazole and 2-(3-methylbutyl)xylylimidazole
are exemplified.
[0059] Other exemplary compounds belonging to the general formula
(5), for instance, include 2-n-propyl-methylbenzimidazole,
2-n-propyl-dimethylbenz- imidazole, 2-n-butyl-methylbenz-imidazole,
2-n-butyl-dimethylbenzimidazole- , 2-n-pentyl-methylbenzimidazole,
2-n-pentyl-dimethylbenzimidazole, 2-n-hexyl-methylbenzimidazole,
2-n-hexyl-dimethylbenz-imidazole, 2-n-heptyl-methylbenzimidazole,
2-n-heptyl-dimethylbenzimidazole, 2-n-octyl-methylbenzimidazole,
2-n-octyl-dimethylbenzimidazole, 2-n-nonyl-methylbenzimidazole,
2-n-nonyl-dimethylbenzimidazole, 2-n-decyl-methylbenz-imidazole,
2-n-decyl-dimethylbenzimidazole, 2-n-undecyl-methylbenzimidazole,
2-n-undecyl-dimethylbenzimidazole, 2-n-dodecyl-methylbenzimidazole,
2-n-dodecyl-dimethylbenz-imidazole,
2-n-tridecyl-methylbenzimidazole,
2-n-tridecyl-dimethylbenzimidazole,
2-n-tetradecyl-methylbenzimidazole,
2-n-tetradecyl-dimethylbenzimidazole,
2-n-pentadecyl-methylbenzimidazole,
2-n-pentadecyl-dimethylbenzimidazole,
2-n-hexadecyl-methylbenzimidazole,
2-n-hexadecyl-dimethyl-benzimidazole,
2-n-heptadecyl-methylbenzimidazole,
2-n-heptadecyl-dimethylbenzimidazole,
2-isopropyl-methylbenz-imidazole,
2-isopropyl-dimethylbenzimidazole, 2-isobutyl-methylbenzimidazole,
2-isobutyl-dimethylbenzimidazole, 2-sec-butyl-methylbenzimidazole,
2-sec-butyl-dimethylbenz-imidazole,
2-tert-butyl-methylbenzimidazole, 2-tert-dimethylbenzimidazole,
2-isopentyl-methylbenzimidazole, 2-isopentyl-dimethylbenzimidazole,
2-neopentyl-methylbenz-imidazole,
2-neopentyl-dimethylbenzimidazole,
2-tert-phenyl-methylbenzimidazole,
2-tert-phenyl-dimethylbenzimidazole, 2-isohexyl-methylbenzimidazole
and 2-isohexyl-dimethylbenzimidazole.
[0060] Preferred compounds that belong to the general formula (4)
not encompassed in the aforesaid general formulae (5) to (7), for
instance, include 6-ethoxy-2-isopropylbenzimidazole,
6-amino-2-isooctylbenz-imidazo- le,
4,6-diacetyl-2-isobutylbenzimidazole,
4-benzoyl-6-carbamoyl-2-n-propyl- benzimidazole,
4,7-dimethoxycarbonyl-2-n-eicosabenzimidazole,
6-methoxy-carbonyl-2-isopropylbenzimidazole,
4,5-dimethyl-7-acetyl-2-hexy- lbenzimidazole,
4-chloro-6-n-heptyl-7-methoxy-2-ethylbenzimidazole,
4,6-difluoro-5-formyl-2-n-nonylbenzimidazole and
6-carbamoyl-4,7-diethoxy- -2-isobutylbenzimidazole as well as their
salts.
[0061] More preferable compounds belonging to the aforesaid general
formulae (1) and (4) to (7), for instance, include
6-methyl-2-n-propylbenzimidazole,
4,5,6,7-tetramethyl-2-n-hexylbenzimidaz- ole,
4,5,6,7-tetramethyl-2-n-propylbenz-imidazole,
2-(3-methylbutyl)methyl- benzimidazole,
2-(3-methylbutyl)dimethylbenzimidazole,
2-(3-methylbutyl)benz-imidazole, 2-(1-ethylpentyl)benzimidazole,
2-(1-ethylpentyl)tosylimidazole, 2-(1-methylpropyl)benzimidazole,
5,6-dichloro-2-n-hexylbenzimidazole,
6-diethylamino-2-n-decylbenzimidazol- e,
6-hydroxy-2-n-eicosabenzimidazole,
4,7-dicyano-2-n-octylbenzimidazole, 6-nitro-2-ethylbenzimidazole
and compounds shown in Tables 1 and 2 given below.
[0062] Of the aforesaid compounds,
6-methyl-2-n-propylbenz-imidazole,
4,5,6,7-tetramethyl-2-n-propylbenzimidazole,
5,6-dichloro-2-n-hexylbenzim- idazole,
6-diethylamino-2-n-decylbenzimidazole, 6-hydroxy-2-n-eicosabenzim-
idazole, 4,7-dicyano-2-n-octylbenzimidazole and
6-nitro-2-ethyl-benzimidaz- ole belong to the general formula (4)
not encompassed in the aforesaid general formulae (5) to (7).
1TABLE 1 Benzimidazole Compounds 1 2-n-propyl-methylbenzimidazole 2
2-n-propyl-dimethylbenzim- idazole 3 2-n-butyl-methylbenzimidazole
4 2-n-butyl-dimethylbenzimidazole 5 2-n-pentyl-methylbenzimidazole
6 2-n-pentyl-dimethylbenzimidazole 7 2-n-hexyl-methylbenzimidazole
8 2-n-hexyl-dimethylbenzimidazole 9 2-n-heptyl-methylbenzimidazole
10 2-n-heptyl-dimethylbenz- imidazole 11
2-n-octyl-methylbenzimidazole 12 2-n-octyl-dimethylbenzimidazole 13
2-n-nonyl-methylbenzimidazole 14 2-n-nonyl-dimethylbenzimidazole 15
2-n-decyl-methylbenzimidazole 16 2-n-decyl-dimethylbenzimidazole 17
2-n-undecyl-methylbenzimidazole 18
2-n-undecyl-dimethylbenzimidazole 19 2-n-dodecyl-methylbenzimidaz-
ole 20 2-n-dodecyl-dimethylbenzimidazole 21
2-n-tridecyl-methylbenzimidazole 22 2-n-tridecyl-dimethylbenzimid-
azole 23 2-n-tetradecyl-methylbenzimidazole 24
2-n-tetradecyl-dimethylbenzimidazole 25 2-n-pentadecyl-methylbenz-
imidazole 26 2-n-pentadecyl-dimethylbenzimidazole 27
2-n-hexadecyl-methylbenzimidazole 28 2-n-hexadecyl-dimethylbenzim-
idazole 29 2-n-heptadecyl-methylbenzimidazole 30
2-n-heptadecyl-dimethylbenzimidazole
[0063]
2TABLE 2 Benzimidazole Compounds 1 2-(2-methylethyl)-benzimidazole
2 2-(2-methylpropyl)-benzi- midazole 3
2-(1-methylbutyl)-benzimidazole 4 2-(1-ethylpropyl)-benzimidazole 5
2-(1-ethylpropyl)-methybenzimid- azole 6
2-(2-metylbutyl)-benzimidazole 7 2-(3-methylbutyl)-benzimidazole 8
2-(1-methylpentyl)-benzimidazol- e 9
2-(1-propylbutyl)-benzimidazole 10 2-(1-ethylpentyl)-benzimidazole
11 2-(1-ethylpentyl)-methylbenzim- idazole 12
2-(1-ethylpentyl)-dimethylbenzimidazole 13
2-(2-methyl-4,4-dimethylpentyl)-benzimidazole 14
2-n-butyl-methylbenzimidazole 15 2-n-butyl-benzimidazole 16
2-n-pentyl-benzimidazole 17 2-n-hexyl-benzimidazole 18
2-n-heptyl-benzimidazole 19 2-n-octyl-benzimidazole 20
2-n-nonyl-benzimidazole 21 2-n-nonyl-methylbenzimidazole 22
2-n-nonyl-dimethylbenzimidazole 23 2-(2,2,3,3)-tetramethylprop-
yl)-benzimidazole
[0064] In the present invention, the preferred compounds belonging
to the aforesaid general formula (2) are represented by the
following general formula (8).
[0065] Formula (8) 13
[0066] Here R.sub.51 is an alkyl group, a phenyl group, an
alkylphenyl group and a phenylalkyl group with the proviso that
when R.sub.51 represents two or more groups, they may be different
from or identical with each other, n is an integer of 0 to 3, and m
is an integer of 0 to 3.
[0067] Compounds having the following general formula (9), too, are
exemplified as the preferred compounds belonging to the aforesaid
formula (2).
[0068] Formula (9) 14
[0069] Here R.sub.41 is a straight-chain or branched-chain alkyl
group having 1 to 7 carbon atoms, a halogen atom, an amino group, a
hydroxy group, a cyano group, a nitro group, a lower alkoxy group,
an acetyl group, a benzoyl group, a carbamoyl group, a lower
alkoxycarbonyl group, a formyl group or a carboxyl group with the
proviso that when R.sub.41 represents two or more groups, they may
be different from or identical with each other, R.sub.52 is a
straight-chain or branched-chain alkyl group having 1 to 7 carbon
atoms, a halogen atom, an amino group, a hydroxy group, a cyano
group, a nitro group, a lower alkoxy group, an acetyl group, a
benzoyl group, a carbamoyl group, a lower alkoxycarbonyl group, a
formyl group or a carboxyl group with the proviso that when
R.sub.52 represents two or more groups, they may be different from
or identical with each other, n and p are each an integer of 0 to
4, and m is an integer of 0 to 10.
[0070] The preferred compounds belonging to this formula (9) are
exemplified by those having the following general formula (10).
[0071] Formula (10) 15
[0072] Here R.sub.42 is a lower alkyl group with the proviso that
when R.sub.42 represents two groups, they may be different from or
identical with each other, R.sub.53 is a lower alkyl group with the
proviso that when R.sub.53 represents two groups, they may be
different from or identical with each other, n and m are each an
integer of 0 to 2.
[0073] Exemplary compounds are 2-phenyl-methylbenzimidazole,
2-phenyl-dimethylbenzimidazole, 2-tosyl-methylbenz-imidazole,
2-tosyl-dimethylbenzimidazole, 2-xylyl-methyl-benzmidazole,
2-xylyl-dimethylbenzimidazole, 2-mesityl-dimethylbenzimidazole and
2-mesityl-methylbenzimidazole.
[0074] Other preferable exemplary compounds belonging to the
aforesaid general formula (9) are 2-(8-phenylocytl)benzimidazole,
5,6-dimethyl-2-(2-phenylethyl)benzimidazole,
4-chloro-2-(3-phenylporpyl)b- enzimidazole,
6-dimethylamino-2-(9-phenylnonyl)benzimidazole,
4,7-dihydroxy-2-benzyl-benzimidazole,
4-cyano-2-(6-phenylhexyl)benzimidaz- ole,
5,6-dinitro-2-benzylbenzimidazole,
4,7-diethoxy-2-(2-henylethyl)benzi- midazole,
6-amino-2-(4-phenylbutyl)benzimidazole, 6-acetyl-2-benzyl-benzim-
idazole, 4-benzoyl-2-(5-phenylpentyl)benzimidazole,
6-carbamoyl-2-(7-phenylheptyl)benzimidazole,
6-ethoxycarbonyl-2-benzylben- zimidazole,
4,5,6-trimethoxy-2-(2-phenylethyl)benzimidazole,
5,6-dimethyl-7-benzoyl-2-(3-phenylpropyl)benzimidazole,
4,5-dichloro-6-n-butyl-2-(9-phenylnonyl)benzimidazole,
4-fluoro-6-formyl-2-benzyl-benzimidazole,
6-carbamoyl-5-ethoxy-2-(10-phen- yldecyl)benzimidazole,
5,6-dimethyl-2-{(4-methoxyphenyl)butyl}benzimidazol- e,
6-chloro-2-{(2-nitrophenyl)ethyl}benzimidazole,
6-carboethoxy-2-(3-buro- mobenzyl)benz-imidazole,
4-hydroxy-2-{(4-cyanophenyl)propyl}benz-imidazole- ,
6-dimethylamino-2-{(4-formylphenyl)propyl}benz-imidazole,
6-benzoyl-2-{(4-tert-butylphenyl)ethyl}benz-imidazole,
2-{2-acetylphenyl}pentyl}benzimidazole and
6-carbamoyl-2-{(2,4-dihydroxyp- henyl)ethyl}benzimidazole.
[0075] More preferred compounds belonging to the aforesaid general
formulae (2) and (8) to (10), for instance, are
2-(8-phenyloctyl)benzimid- azole,
4-chloro-2-(3-phenypropyl)benzimidazole,
6-dimethylamino-2-(9-pheny- lnonyl)benz-imidazole,
4,7-dihydroxy-2-benzylbenzimidazole,
4-cyano-2-(6-phenylhexyl)benzimidazole,
5,6-dinitro-2-benzylbenz-imidazol- e,
4,7-diethoxyl-2-(2-phenylethyl)benzimidazole,
5,6-dimethyl-2-{(4-methox- yphenyl)butyl}benzimidazole,
6-chloro-2-{(2-nitrophenyl)ethyl}benzimidazol- e,
6-carboethoxy-2-(3-bromobenzyl)benzimidazole,
4-hydroxy-2-{(4-cyanophen- yl)propyl}benzimidazole,
6-dimethylamino-2-{(4-formylphenyl)propyl}benzimi- dazole,
6-benzoyl-2{(4-tert-butylphenyl)ethyl}benzimidazole,
2-{(2-acetylphenyl)pentyl}benzimidazole,
6-carbamoyl-2-{(2,4-dihydroxyphe- nyl)ethyl}benzimidazole and
5,6-dimethyl-2-(2-phenylethyl)benzimidazole as well as compounds
enumerated in Tables 3 and 4 given just below.
3TABLE 3 Benzimidazole Compounds 1
2-phenylmethyl-methylbenzimidazole 2
2-phenylmethyl-dimethylbenzimidazole 3 2-tosyl-methylbenzimidazol-
e 4 2-tosyl-dimethylbenzimidazole 5 2-xylyl-methylbenzimidazole 6
2-xylyl-dimethylbenzimidazole 7 2-mesityl-methylbenzimidazole 8
2-mesityl-dimethylbenzimidazo- le 9
2-tert-phenyl-methylbenzimidazole 10
2-tert-phenyl-dimethylbenzimidazole
[0076]
4TABLE 4 Benzimidazole Compounds 1
2-(4-tert-butylphenyl)-benzimidazole 2
2-(4-hexylphenyl)-benzimidazole 3 2-(2,4,6-trimethylphenyl)-benzi-
midazole 4 2-(4-butylphenyl)-benzimidazole 5
2-(4-pentylphenyl)-benzimidazole 6 2-(4-hexylphenyl)-benzimidazol-
e 7 2-(2-phenylethyl)-benzimidazole 8
2-(2-phenylethyl)-methylbenzimidazole 9 2-(4-ethylphenyl)-benzimi-
dazole 10 2-tosyl-benzimidazole 11 2-(2-biphenyl)-benzimid- azole
12 2-(4-biphenyl)-benzimidazole 13 2-(2-benzylphenyl)-benzimidazole
14 2-(2-phenetylphenyl)-benzimid- azole 15
2-(4-ethyl-4-biphenyl)-benzimidazole 16
2-(1-phenyl-2-methylbutyl)-benzimidazole 17
2-(1-phenylpropyl)-benzimidazole 18 2-{1-(4-isobutylphenyl)ethyl}-
-benzimidazole 19 2-(1,1-diphenylmethyl)-benzimidazole 20
2-(1,1-diphenylethyl)-benzimidazole 21 2-(2,2-diphenylethyl)-benz-
imidazole 22 2-triphenylmethyl-benzimidazole 23
2-(2,2,2-triphenylethyl)-benzimidazole 24 2-(4-phenylbutyl)-benzi-
midazole 25 2-(5-phenylpentyl)-benzimidazole 26
2-(3-phenylpropyl)-benzimidazole 27 2-(2-phenylpropyl)-benzimidaz-
ole 28 2-(1-phenylethyl)-benzimidazole 29
2-n-phenylmethyl-benzimidazole
[0077] In the present invention, more preferred compounds included
in the aforesaid general formula (3), for instance, are those
listed in the following Table 5. It is here preferred that R be a
methyl group and n be an integer of 0 to 2.
5TABLE 5 Benzimidazole Compounds 1 2-cyclobutyl-benzimidazole 2
2-cyclopentyl-benzimidazole 3 2-cyclohexyl-benzimidazole 4
2-cyclohexyl-methylbenzimida- zole 5
2-cyclohexyl-dimethylbenzimidazole 6 2-cyclobutyl-benzimidazole 7
2-(1-cycloheptyl)-benzimidazole 8
2-(1-methylcyclopropyl)-benzimidazole 9
2-(2-methylcyclopropyl)-benzimidazole 10 2-(1-methylcyclohexyl)-b-
enzimidazole 11 2-(2-methylcyclohexyl)-benzimidazole 12
2-(3-methylcyclohexyl)-benzimidazole 13 2-(4-methylcyclohexyl)-be-
nzimidazole 14 2-cyclopentyl-methylbenzimidazole 15
2-(2-cyclopentylethyl)-benzimidazole 16 2-(2-cyclohexylethyl)-ben-
zimidazole 17 2-(3-cyclohexylpropyl)-benzimidazole
[0078] In the present invention, at least one compound selected
from the group consisting of the compounds represented by the
aforesaid general formulae (1) and (3) is used in combination with
at least one compound represented by the aforesaid general formula
(2). Accordingly, the compounds belonging to the aforesaid
generally formulae included in the aforesaid respective general
formulae as well as exemplary compounds thereof, too, may be used
in combination. At least one compound selected from the group
consisting of those represented by the aforesaid general formulae
(1) and (3) should be used in the proportion on a mass basis of 1:2
to 5:1, and preferably 1:1 to 3:1 with respect to at least one
compound represented by the aforesaid general formula (2). In other
words, the former-to-latter ratio should be in the range of 0.5 to
5, and preferably 1 to 3. When the amount of the former compound is
larger than that upper limit or the amount of the latter is smaller
than that lower limit, a protective film can be more easily formed
and so a thicker film can be formed on a copper foil. Too thick a
film is a less-soluble, difficult-to-remove flux fraction that may
otherwise cause nonwetting of solder. Conversely, when the amount
of the former compound is smaller than that lower limit or the
amount of the latter is larger than that upper limit, the formation
of a protective film can be less likely, and so the effect on
prevention of oxidation of the copper foil becomes slender on
account of the formation of a defective film, again resulting in
possible nonwetting of solder even when some flux is used.
[0079] In the present invention, the wetting coverage and
solderability of fused solder upon fusion of a solder paste film
can be improved by using an iodine-based compound in combination
with the benzimidazole compound. Exemplary iodine-based compounds
are hydriodic acid or its metal salts such as its alkaline metal
salts, e.g., potassium iodide and its heavy metal salts, e.g., zinc
iodide and copper iodide, and an iodized organic acid, for
instance, an iodized lower aliphatic monobasic acid such as
iodopropionic acid and its polybasic acid.
[0080] It is preferred that the iodine-based compound be added in
an amount of 0.05% to 5% into the water-soluble preflux. In the
present disclosure, "%" is given by mass.
[0081] To enhance the solubility of the iodine-based compound and
increase the amount of the iodine-based compound to be added, it
should preferably be used in combination with an amine-based
compound, especially an amine-based compound containing an acidic
group such as amino acid, thereby making much better the wetting
coverage and solderability of fused solder upon fusion of a solder
paste film. This amine-based compound should preferably be added in
an amount of 0.01% to 3% into the water-soluble preflux.
[0082] For the amine-based compound containing an acidic group, it
is acceptable to make use of the following compounds referred to as
solubilizers.
[0083] For use, the water-soluble preflux is conveniently placed in
a state wherein the so-called benzimidazole compounds represented
by the aforesaid general formulae (1) to (10) are dissolved or
emulsified in solvents, for which water or water-miscible solvents
or mixtures of such solvents may be exemplified. In this case,
acids are used as solubilizers because the benzimidazole compounds
are generally insoluble in water. For such acids, it is preferable
to use compounds having at least one of hetero-cyclic rings
including rings containing a primary amino group, a secondary amino
group, a tertiary amino group and a nitrogen atom capable of
forming a water-soluble salt of the acids and having an acidic
group. More preferably, however, use should be made of at least one
compound selected from the group consisting of the compounds
represented by the aforesaid general formulae (11) to (16),
L-theanine, pyroglutamic acid, pyrrolidine-2,4-dicarboxylic acid,
folic acid, DL-threonine, L-threonine, L-tryptophan,
L-phenylalanine and quinaldinic acid as well as their derivatives.
Exemplary compounds represented by the aforesaid general formulae
(11) to (16), L-theanine and so on are listed in order in the
following Tables 6 to 12.
6 TABLE 6 16 anthranilic acid
[0084]
7TABLE 7 17 isonicotinic acid 18 2-chloronicotinic acid 19
chelidamic acid 20 citrazinic acid 21 3-pyridineacetic acid 22
picolinic acid 23 nicotinic acid
[0085]
8TABLE 8 24 : 2,3-pyradinecarboxylic acid 25 :
pyradinemonocarboxylic acid
[0086]
9TABLE 9 26 : pyrrolidine-2,4-carboxylic acid
[0087]
10TABLE 10 27 : alanine 28 : L-glutamic acid
NH.sub.2--(CH.sub.2).sub.2--COOH : .gamma.-aminobutyric acid
NH.sub.2--(CH.sub.2).sub.3--COOH : .epsilon.-aminocaproic acid 29 :
L-aspartic acid NH.sub.2--(CH.sub.2).sub.11--COOH : aminododecanoic
acid 30 : iminodiacetic acid
[0088]
11TABLE 11 31 : ethylenediaminetetraacetic acid
[0089]
12TABLE 12 32 : L-theanine 33 : pyroglutamic acid 34 : folic acid
35 : DL-threonine 36 : L-threonine 37 : L-tryptophan 38 :
L-phenylalanine 39 : quinaldinic acid
[0090] These acidic group-containing amine-based compounds may be
used in combination of two or more. These compounds, when used as
solubilizers, are added in an amount of 0.01 to 20%, and preferably
0.1 to 5% to water.
[0091] More preferable among these compounds are alanine,
aminododecanoic acid, imiodiacetic acid and anthranilic acid.
[0092] Using the aforesaid acidic acid-containing amine-base
compound as the solubilizer is preferable because there is no
erosion of a precoated solder layer for parts having a narrow pitch
lead such as QFPs or a solder layer at the time of soldering. When
the primary purpose of using the iodine-based compound is to
improve the aforesaid wetting coverage and soliderability of
solder, however, other currently available acids, too, may be used
alone or in combination with the aforesaid amine-based compounds.
To this end use may be made of organic acids such as formic acid,
acetic acid, propionic acid, butyric acid, glycolic acid, lactic
acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid,
bromoacetic acid, dibromoacetic acid, fluoroacetic acid,
difuloroacetic acid, trifluroacetic acid, oxalic acid, malonic
acid, succinic acid, adipic acid, malic acid, tartaric acid, citric
acid, maleic acid, fumaric acid, p-toluenesulfonic acid,
methanesulfonic acid, and inorganic acids such as hydrochloric
acid, sulfuric acid, phosphoric acid, phosphorous acid,
hypophosphorous acid and nitric acid, among which formic acid and
tartaric acid are more preferred.
[0093] The water-miscible solvent, for instance, may be any solvent
capable of being mixed with water or any solvent of high solubility
in water. Exemplary solvents, which may be added in suitable
amounts if required, are methanol, ethanol, isopropanol, butanol,
acetone, methyl ethyl ketone, tetrahydrofuran, dioxane,
dimethylsulfoxide and dimethylformamide.
[0094] The content of the aforesaid benzimidazole compound of the
invention in the water-soluble preflux according to the invention
should be in the range of 0.05 to 30%, and preferably 0.1 to 5%. At
less than 0.05% any effective rust-preventive film cannot be
formed, and at greater than 30% much insolubles remain and any
economical merit is not achieved.
[0095] In addition, the water-soluble preflux according to the
present invention contain an additive for assisting in the
formation of a complex film with copper, which is exemplified by
metal compounds such as copper formate, cupric chloride, cuprous
chloride, copper oxalate, copper acetate, copper hydroxide, copper
oxide, cuprous oxide, cupric oxide, copper carbonate, copper
phosphate, copper sulfate, manganese formate, manganese chloride,
manganese oxalate, manganese sulfate, lithium, beryllium,
potassium, magnesium, zinc acetate, lead acetate, hydrogenated
zinc, ferrous chloride, ferric chloride, ferrous oxide, ferric
oxide, copper iodide, cuprous bromide and cupric bromide. These
additives may be used alone or in combination of two or more, and
added in an amount of 0.01 to 10%, and preferably 0.1 to 5% with
respect to the treating solution. However, care must be taken of
the use of the additive to form a complex with copper, because an
additional film may be formed on gold plating on a printed circuit
board although depending on conditions, resulting in discoloration
of the gold plating.
[0096] It is also preferable to use a metal ion-containing buffer
solution in which the aforesaid metal compound is used. Typical
bases to this end, for instance, include ammonia, diethylamine,
triethylamine, diethanolamine, triethanolamine, monoethanolamine,
dimethylethanolamine, diethylethanolamine, isopropylethanolamine,
sodium hydroxide and potassium hydroxide.
[0097] All things considered, it is preferable that the
water-soluble preflux of the present invention should contain at
least one compound selected from the group consisting of those
represented by the aforesaid general formulae (1) and (3), at least
one compound represented by the aforesaid general formula (2), the
aforesaid iodine-based compound and at least one of the aforesaid
metal compounds (or a buffer solution containing metal ions of at
least one of the aforesaid metal compounds). More preferably, the
water-soluble preflux of the invention should contain a solubilizer
comprising at least one compound selected from the group consisting
of the compounds represented by the aforesaid general formulae (11)
to (16), L-theanine, pyroglutamic acid,
pyrrolidine-2,4-dicarboxylic acid, folic acid, DL-threonine,
L-threonine, L-tryptophan, L-phenylalanine and quinaldinic acid as
well as their derivatives.
[0098] To coat the water-soluble preflux of the present invention
on the printed circuit board to be subjected to rust-preventive
treatment, so that a rust-preventive film is formed thereon, the
surface of a copper layer in the printed circuit board is
pretreated by polishing, degreasing, pickling and rinsing. Then,
the printed circuit board is immersed in the water-soluble preflux
at 0 to 100.degree. C. for a few seconds to a few tens of minutes,
and preferably at 20 to 50.degree. C. for 5 seconds to 1 hour and
preferably for 10 seconds to 10 minutes. The treating solution used
herein should be acid or have a pH value of preferably up to 5.0
(not greater than 5.0).
[0099] Thus, the benzimidazole compound according to the present
invention is deposited onto the copper layer. The higher the
treating temperature and the longer the treating time, the more the
amount of the compound deposited is. In this case, it is more
preferable to make use of ultrasonic waves.
[0100] It is appreciated that other coating means, for instance,
spraying, brushing or roller coating may also be used. The thus
obtained rust-preventive film can exhibit extremely satisfactory
solderability even at high temperature and high humidity.
[0101] One typical embodiment of the present invention wherein a
printed circuit board is fabricated is now explained. This
embodiment uses at least three steps as mentioned just below.
[0102] At the first step, a board comprising a copper-clad laminate
board is provided by etching with a circuit pattern comprising
predetermined circuit interconnections and including soldering
lands for soldering a chip part to the board, and a solder resist
is put over a portion of the board other than the soldering
lands.
[0103] At the second step, the surface of copper under the circuit
pattern is pretreated by polishing, degreasing, pickling (micro
etching) and rinsing.
[0104] At the third step, the exposed surface of copper unders the
soldering lands is coated with the water-soluble flux comprising at
least one compound selected from the group consisting of those
represented by the aforesaid general formulae (1) and (3), at least
one compound represented by the aforesaid general formula (2) and
at least one of the aforesaid iodine-based compounds, followed by
drying. Preferably in this embodiment, this water-soluble preflux
is solubilized by at least one of the compounds represented by the
aforesaid formulae (11) to (16) or the like.
[0105] Thus, the obtained preflux film prevents oxidation of the
copper surface and functions well as a rust-preventive film, even
when the compounds contained in the water-soluble flux and
represented by the aforesaid general formulae (1) to (16) or other
compounds have acid roots. The resulting printed circuit board is
coated at the aforesaid soldering lands with a solder paste
(containing solder powders and a flux) with or without a post-flux
coated thereon, so that the electrodes of the aforesaid chip part
are soldered thereto by a reflow soldering process. It is here
acceptable that a circuit board having a solder precoat layer and
ordinary soldering lands is similarly coated or otherwise treated
with the aforesaid water-soluble preflux, and the aforesaid chip
part and a narrow-pitch part are located at given positions so that
by means of a reflow soldering process, the lead of the
narrow-pitch part is soldered to the solder precoat layer of a
narrow-pitch pad and the electrodes of the aforesaid chip part are
soldered to the aforesaid soldering land.
[0106] The present invention will now be explained more
specifically with reference to some examples.
EXAMPLE 1
[0107] One (1.0) gram of 6-methyl-2-n-propylbenzimidazole, 1.0 gram
of 2-phenyl-methylbenzimidazole, 0.1 gram of copper sulfate, 0.5
gram of potassium iodide and 0.1 gram of 25% ammonia water were
added and incorporated in this order into 100 grams of a 2% by mass
aqueous solution of formic acid, thereby preparing a water-soluble
preflux.
[0108] Immersed at 50.degree. C. for 2 minutes in this
water-soluble preflux was a test piece that was obtained by
cleaning a JIS Z 3197 prescribed comb board (having copper foil
electrodes) by degreasing, soft etching and rinsing.
[0109] After this, the test piece was rinsed with water, and then
dried in warm air, whereupon the test piece was passed through an
air reflow furnace where it was heated once, twice, and thrice to
force the copper foil surface to degrade. A solder paste
(comprising solder powders of Sn/Pb=63/37 and a flux containing
rosin and an activator) was fed by a printing process to each test
piece subjected to degradation-by-heating treatment and a test
piece not subjected to degradation-by-heating treatment, which were
then heated through an air reflow furnace so that the solder
powders were fused as in the case of actual soldering, and then
cooled down. The length of the wetting coverage of solder over the
copper foil of the post-cooling test piece was measured. The
results are shown in Table 13.
EXAMPLE 2
[0110] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that
2-n-octylbenzimidazole was used instead of
6-methyl-2-n-propylbenzimidazole. The results are shown in Table
13.
EXAMPLE 3
[0111] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that
4-chloro-2-(3-phenylprop- yl)benzimidazole was used in place of
2-phenyl-methylbenzimidazole. The results are shown in Table
13.
EXAMPLE4
[0112] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that
3-iodopropionic acid was used instead of potassium iodide. The
results are shown in Table 13.
EXAMPLE 5
[0113] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that the amount of
potassium iodide was changed to 2.0 grams with the addition of 1.0
gram of alanine. The results are shown in Table 13.
EXAMPLE 6
[0114] The length of the wetting coverage of fused solder powders
was measured as in Example 5 with the exception that anthranilic
acid was used for alanine. The results are shown in Table 13.
EXAMPLE 7
[0115] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that no copper
sulfate was used. The results are shown in Table 13.
REFERENCE EXAMPLE 1
[0116] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that
6-methyl-2-n-propylbenzi- midazole was not used. The results are
shown in Table 13.
REFERENCE EXAMPLE 2
[0117] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that
2-phenyl-methylbenzimida- zole was not used. The results are shown
in Table 13.
REFERENCE EXAMPLE 3
[0118] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that no potassium
iodide was used. The results are shown in Table 13.
REFERENCE EXAMPLE 4
[0119] The length of the wetting coverage of fused solder powders
was measured as in Example 1 with the exception that potassium
chloride was used for potassium iodide. The results are shown in
Table 13.
[0120] As a result of SEM (scanning electron microscope) evaluation
of the surfaces of the test pieces of Examples 5 and 6 covered with
the water-soluble preflux, no change was found at all, indicating
that both the test pieces had sufficient soldering strength upon
soldering of the chip parts with no occurrence of any soldering
bridge.
13TABLE 13 Length of the wetting coverage of fused solder of solder
powders in the solder paste films Testing Inventive Example Ref.
Ex. Conditions 1 2 3 4 5 6 7 1 2 3 4 (A) 6.0 6.0 6.0 5.8 6.5 6.5
6.0 4.0 4.5 2.8 3.2 (B) 3.5 3.8 3.8 3.5 4.0 4.0 3.5 2.8 3.3 1.8 2.0
(C) 3.2 3.5 3.2 3.2 3.8 3.5 3.2 2.2 3.0 1.5 1.5 (D) 2.8 3.0 2.8 3.0
3.5 3.2 2.8 1.5 2.2 1.2 1.2
[0121] Length measured in mm
[0122] (A) Measured before the degradation by heating
[0123] (B) Measured after the 1st degradation by heating
[0124] (C) Measured after the 2nd degradation by heating
[0125] (D) Measured after the 3rd degradation by heating
[0126] From the results of Table 13, i.e., from comparisons of
Inventive Examples 1-4 and 7 with Inventive Examples 5 and 6, it is
found that before the degradation by heating, 6.5 mm in the latter
examples is an about 8% better than the best 6.0 mm in the former
examples and even after the 3rd degradation by heating, the lowest
in the latter is an about 7% better than the highest in the former;
the more the iodine-based compound used, the higher the effects and
such effects are much more enhanced by the combined use of that
compound and the amino acid.
[0127] From comparisons of Inventive Examples 1 and 7 with
Reference Examples 1 and 2, it is found that before the degradation
by heating, the figures in Inventive Examples 1 and 7 are an about
27% better than the higher figure in Reference Examples 1 and 2 and
after the 3rd degradation by heating, the former are an about 27%
better than the latter; the synergistic effect by the combined use
of two separate benzimidazoles is much more higher than the effect
resulting from their sole use.
[0128] From comparisons of Inventive Examples 1 and 7 with
Reference Examples 3 and 4, it is found that before the degradation
by heating, the figures in Inventive Examples 1 and 7 are an about
88% better than the higher figure in Reference Examples 3 and 4 and
after the 3rd degradation by heating, the former is at least
two-fold better than the latter; as the degradation of the copper
foil by heating proceeds, the effect of using the iodine-based
compound becomes more prominent. It is noted that Reference
Examples 1 and 2 are all better than Reference Examples 3 and 4;
however, they are not known so far in the art and so are provided
for reference.
[0129] As the wetting coverage of fused solder over soldering lands
is satisfactory, the fused solder is well wetted to and spread over
the whole surface of the soldering lands so that the adhesion power
of the soldering lands to a metallic surface can increase.
Moreover, the fused solder is kept from concentrating on the middle
of a certain soldering land due to its surface tension into a
droplet, and so from going over the adjacent soldering lands and
coming into contact with fused solder similarly formed thereon.
This could be one possible explanation of why any soldering bridge
is avoided, although not necessarily bound thereto.
[0130] Thus, as the wetting coverage of fused solder over the
soldering lands is satisfactory, the area of the fused solder
spread over the soldering lands is enlarged and, accordingly, the
adhesion power of solder to the soldering lands is so increased
that the soldering strength for electronic parts can be enhanced.
Thus, even when the amount of the solder paste to be coated is
reduced, the desired soldering strength is obtainable.
[0131] The more preferable compounds among the acidic
group-containing compounds and iodine compounds represented by the
aforesaid general formulae (1), (4) to (7) as well as the aforesaid
general formulae (2), (8) to (10) and (11) to (16) and compounds
similar to or analogous with the compounds used in Inventive
Examples 1 to 7, too, may be used according to these examples.
[0132] According to the present invention where given two types of
benzimidazoles are used in combination with the iodine-based
compound, the fused solder can be better wetted to and spread over
soldering lands in general, and a soldering land array having a
narrow spacing, as compared with the use of each benzimidazole
compound in combination with the diode-based compound, to say
nothing of the use of each in combination with a compound other
than the iodine-based compound, e.g., a chloride. Moreover, the
fused solder can be well wetted to and spread over soldering lands
that have degraded upon heated to high temperature for the purpose
of both-sided mounting, so that the incidence of soldering bridges
can be reduced, making soldering strength sufficient and decreasing
the incidence of poor soldering, resulting in productivity
improvements. Thus, the present invention provides a water-soluble
preflux that permits a heat-resistant film showing very excellent
humidity resistance even after exposed to high humidity to be
formed on the surface of copper or a copper alloy for circuit
patterns on printed circuit board and to be much improved in terms
of the protection and solderability of printed circuit boards upon
part mounting, a printed circuit board and a surface treatment
process for metals on printed circuit boards.
[0133] The present invention also provides a water-soluble preflux
that can be used in combination with an acidic group-containing
amine-based compound or other amine-based compound to make a
benzimidazole-based compound soluble without recourse to
conventionally used acids, so that the amount of the iodine-based
compound used can be increased thereby achieving the aforesaid
advantages more satisfactorily, and solve problems with the
oxidation of solder, soldering strength drops due to erosion of
lead, etc. which are caused when acids are used as solubilizes as
usual, a printed circuit board and a surface treatment process for
metals on printed circuit boards.
[0134] Furthermore, the present invention provides a water-soluble
preflux that can be fabricated and used as is the case with
conventional water-soluble prefluxes using benz-imidazole-based
compounds, permits each component to keep its stability intact
irrespective of temperature changes and prevents working
environments from becoming worse due to volatile acids, a printed
circuit board and a printed circuit board fabrication process.
* * * * *